Boonton 4530 Peak Power Meter User Manual - Manual (Page 40)

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Chapter 3 Boonton Electronics
Operation 4530 Series RF Power Meter
3.10.2 Zero Offset Adjustment. After a CW sensor is connected, and anytime a low-level measurement is about
to be taken, the sensor should be zeroed. To zero a sensor, press the Zero/CAL button to display the Zero/
Calibration menu. Peak sensors may also be zeroed once they have been autocaled, but this is not necessary
immediately following an autocal, since zeroing is performed as part of any autocal process. If more than one
sensor is connected to the 4530, the < and > keys may be used to select the desired sensor. The Zero/Cal menu
is shown in Table 3-4. Connect the sensor to the instrument’s calibrator or to a terminated connector with no
RF present, and use the
∧ and ∨ keys to select Zero Chan, then press Enter/Run to start the process. Zeroing
the sensor takes approximately 20 seconds, and the instrument will display a status line indicating progress.
When zeroing is complete, the sensor can be removed from the calibrator and measurements can be started,
or a Fixed Calibration can be performed to adjust for gain errors.
3.10.3 Fixed Calibration (CW sensors). Fixed calibration adjusts the slope (gain) of the sensor’s shaping curve
by measuring power at a single, reference level (usually 0dBm, or 1mW) from the internal calibrator. To
perform a fixed calibration, connect the sensor to the instrument’s calibrator and press the Zero/CAL key.
Use the
∧∧∧∧∧ ∨∨∨∨
and
∨ keys to select Fixed Cal, and then press Enter/Run to start the process. This will take several
seconds. When fixed calibration is complete, the sensor can be removed from the calibrator and measure-
ments can be taken. Fixed calibration is very fast, and provides good accuracy for many applications.
However, for best accuracy, a step calibration (AutoCal) is recommended when available.
3.10.4 Automatic (step) Calibration. A multi-point step calibration, or autocal uses the 4530’s built-in 50MHz
programmable calibrator or an external Model 2530 1GHz programmable calibrator to step through the entire
power range of the sensor and store a shaping correction at each point. To perform an autocal, connect the
sensor to the instrument’s calibrator and press the Zero/Cal key. Use the
∧∧∧∧∧ ∨∨∨∨
and
∨ keys to select AutoCal, and
then press Enter/Run to start the process. The autocal process takes from one to two minutes, during which
time the instrument will display a status line indicating the current power point being calibrated. When
autocal is complete, the sensor can be removed from the calibrator and measurements can be taken.
3.10.5 Frequency Calibration. If no other calibration factor is entered, the instrument calculates a calibration
factor for the current operating frequency by interpolating between entries from this list. If, however, greater
accuracy is desired, the user may perform a single-point frequency calibration using an external 0 dBm
reference signal at the desired test frequency. To perform a frequency calibration, first make sure the channel’s
operating frequency is set to the frequency of the external reference signal to be used. Connect the sensor to
the reference source, set the source for 0.00 dBm, and press the Zero/Cal key. Use the
∧∧∧∧∧ ∨∨∨∨
and
∨ keys to select
FreqCal, and then press Enter/Run to start the process. The process takes several seconds. When the
frequency calibration is complete, the sensor can be removed from the reference source and measurements
can be taken.
3.10.6 Calibrator Selection. Certain peak power sensors have a video bandwidth that is too high to permit
calibration using the 4530’s built-in 50MHz calibrator. In this case, an external 1GHz calibrator must be used
to autocal the sensor. The Boonton Model 2530 1GHz Programmable Calibrator is designed to connect
directly to the 4530 and operate under instrument control in the same manner as the internal calibrator. (See
Appendix B.) To use an external 2530 calibrator to calibrate sensors, first make sure the 2530 is connected to
the EXT CAL CONTROL connector on the rear of the instrument using a standard RJ-11 type modular
telephone cable (see Figure 3-20). The calibrator’s power must be turned on, and proper connection can be
verified by pressing MainMenu > Calibratr > SelectExt to select the external calibrator, then pressing
MainMenu > Calibratr > ExtStatus to view status information from the 2530. If an error message appears,
check the connections and repeat the process.